This invention is related to the oil and gas industry. Preparing the wellbore and casing surface before placing cement in the annulus is an important step in achieving successful cement bonding between the casing surface, the borehole, and the cement. While drilling operations use drilling fluids (known as mud) to balance formation pressure and carry away drilling debris, cementing operations use a water-based cement that does not adhere well to surfaces coated with oil. To achieve proper bonding between cement and the casing surface, the casing surface should therefore be cleaned of oil-based fluids in order for the water-based cement to adhere properly. To displace and clean the surfaces of oil-based fluids, water-based fluids are pumped through and around a casing and borehole. However, there is a need for determining when the casing surface is clean (also known as being “water-wet”).
One non-invasive technique to determine surface wettability of a surface is by using Electrochemical Impedance Spectroscopy (EIS), which has the potential to be performed at high pressure/high temperature (HPHT) conditions, and which is referred to in U.S. Pat. No. 8,766,641 and US application 2014/0060819. However, the EIS techniques described requires that the system to be in a static condition while the EIS data is being logged. This is a major drawback for using EIS as normal operations need to be halted. Furthermore, both in the field and in the laboratory, the mathematical modeling effort involved in employing EIS may restrict its use by someone who is not an expert in that area of expertise. In addition, the data logging equipment used in EIS is expensive.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.